The present invention relates to an optical disk apparatus, and more particularly to an optical disk apparatus in which a recovery operation in the case where a focus error occurs during a seek operation of moving an optical pickup from a given position of an optical disk to another given position is made faster.
In an optical disk apparatus, when a focus error occurs for any reason during a seek operation of moving an optical pickup from a given position of an optical disk to another given position, a focus search (focusing) is again conducted and the seek operation is then restarted.
In a first related art, a focus search in the case where a focus error has occurred is conducted in the following manner.
A focus search is carried out in the place where the focus error has occurred. Until the focusing is attained, the focus search in the place is retried three times. Only when the focusing is not attained the focusing even after the focus search is retried three times, the optical pickup is moved toward the innermost periphery of the disk, and then the seek operation is again carried out.
In a second related art which is an access method in a CD player disclosed in Unexamined Japanese Patent Publication No. 6-251384A, when an optical pickup (optical head) causes a head jump, the focusing operation is automatically performed. When a head jump occurs during reproduction, a focus search is again conducted in the place. If this focusing is failed, the optical pickup is then moved from the current position toward the outer peripheral side by several millimeters, and a focus search is again conducted. If focusing is not attained even after the process of conducting a focus search with moving the pickup toward the outer peripheral side by several millimeters is performed several times, a process is finally carried out in which the optical pickup is moved to the innermost periphery and then the seek operation is again conducted.
During a seek operation of moving an optical pickup from a given position of an optical disk to another given position, a focus error is mainly caused by a movement of the optical pickup in which the pickup happens to be moved out of an area below the disk, namely, outside of the outer peripheral end of the optical disk for any reason. In such a case, when the related focus search operations such as that described above are conducted, a long time period is required for attaining the focusing.
In the first related art, a focus search is conducted three times in the place where a focus error has occurred. In the case where the optical pickup has been moved to the outside of the optical disk, however, the focusing cannot be attained even by the three retries, and hence the time period for the retries is wasted. In the second related art, the process in which a focus search is again conducted in the place where the focus error has occurred and then conducted with moving the pickup toward the outer peripheral side by several millimeters is repeated several times. During a time period when the process is repeatedly performed, the focusing cannot be made close, and hence the time period is wasted.
An example in which the optical disk apparatus is a CD-ROM drive connected to a personal computer will be considered. When a focus error occurs during a seek operation, it is required to conduct a focus search to attain the focusing, thereby enabling the seek operation to be rapidly restarted. If the seek operation cannot be restarted, there arises a serious situation in which execution of an application software is halted and the personal computer produces an error message.
In both of the above-described related arts, however, there is a problem in that, when a focus error is caused because the optical pickup happens to be moved to the outside of the optical disk, a prolonged time period is required for attaining the focusing and hence the personal computer produces an error message.